The Collaborative International Dictionary of English v.0.48:

Grater \Grat"er\, a. [From Qrate, v.]
   One who, or that which, grates; especially, an instrument or
   utensil with a rough, indented surface, for rubbing off small
   particles of any substance; as a grater for nutmegs.
   [1913 Webster]

WordNet (r) 3.0 (2006):

grater
    n 1: utensil with sharp perforations for shredding foods (as
         vegetables or cheese)